1. Field of Invention
The present invention relates to a method for programming and erasing a non-volatile memory. More particularly, the present invention relates to a method for programming and erasing a non-volatile memory with a nitride tunneling layer.
2. Description of Related Art
The family of the non-volatile memory includes the erasable programmable read-only memory (EPROM) and the electrically erasable programmable read-only memory (E2PROM). Particularly, the E2PROM can be erased and programmed electrically and is capable of retaining data even if the power is turned off, and therefore is widely used in personal computers and in electronic apparatuses.
The E2PROM with a silicon oxide/silicon nitride/silicon oxide (ONO) stacked structure is recently developed, which includes the Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) memory and the nitride read-only memory (NROM). By comparing with the conventional non-volatile memory having a doped polysilicon floating gate, the SONOS memory uses lower voltages for its operation and therefore can be easily scaled down for a higher integration. On the other hand, the NROM is able to prevent a leakage and to store two bits in one memory cell, and therefore has a better performance. A typical NROM is capable of preventing a leakage is because the injected electrons are localized in certain regions in the silicon nitride charge trapping layer. These injected electrons are less likely to locate on the defects in the tunnel oxide layer that would otherwise cause a leakage.
However, since the SONOS memory and the NROM both use silicon oxide as the material of the tunneling layer, the following problems are encountered.
Since silicon oxide has a high energy barrier for an electron and an electron hole, the efficiency of hot carrier (electron or electron hole) injection through the tunnel oxide layer is low when the channel hot carrier injection mechanism is used to program or to erase the SONOS or NROM device. Thus the rates of the programming operation and the erasing operation of the memory device are lowered.